AUTHOR=Li Fei , Guo Dagang , Gao Xiaodong , Zhao Xining 

TITLE=Water Deficit Modulates the CO2 Fertilization Effect on Plant Gas Exchange and Leaf-Level Water Use Efficiency: A Meta-Analysis

JOURNAL=Frontiers in Plant Science

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.775477

DOI=10.3389/fpls.2021.775477

ISSN=1664-462X

ABSTRACT=<p>Elevated atmospheric CO<sub>2</sub> concentrations ([eCO<sub>2</sub>]) and soil water deficits significantly influence gas exchange in plant leaves, affecting the carbon-water cycle in terrestrial ecosystems. However, it remains unclear how the soil water deficit modulates the plant CO<sub>2</sub> fertilization effect, especially for gas exchange and leaf-level water use efficiency (WUE). Here, we synthesized a comprehensive dataset including 554 observations from 54 individual studies and quantified the responses for leaf gas exchange induced by e[CO<sub>2</sub>] under water deficit. Moreover, we investigated the contribution of plant net photosynthesis rate (<italic>P</italic><sub><italic>n</italic></sub>) and transpiration rates (<italic>T</italic><sub>r</sub>) toward WUE in water deficit conditions and e[CO<sub>2</sub>] using graphical vector analysis (GVA). In summary, e[CO<sub>2</sub>] significantly increased <italic>P</italic><sub>n</sub> and WUE by 11.9 and 29.3% under well-watered conditions, respectively, whereas the interaction of water deficit and e[CO<sub>2</sub>] slightly decreased <italic>P</italic><sub>n</sub> by 8.3%. Plants grown under light in an open environment were stimulated to a greater degree compared with plants grown under a lamp in a closed environment. Meanwhile, water deficit reduced <italic>P</italic><sub>n</sub> by 40.5 and 37.8%, while increasing WUE by 24.5 and 21.5% under ambient CO<sub>2</sub> concentration (a[CO<sub>2</sub>]) and e[CO<sub>2</sub>], respectively. The e[CO<sub>2</sub>]-induced stimulation of WUE was attributed to the common effect of <italic>P</italic><sub>n</sub> and <italic>T</italic><sub>r</sub>, whereas a water deficit induced increase in WUE was linked to the decrease in <italic>T</italic><sub>r</sub>. These results suggested that water deficit lowered the stimulation of e[CO<sub>2</sub>] induced in plants. Therefore, fumigation conditions that closely mimic field conditions and multi-factorial experiments such as water availability are needed to predict the response of plants to future climate change.</p>